Carry congestion status in BGP extended community
draft-li-idr-congestion-status-extended-community-00
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| Authors | Zhenqiang Li , Jie Dong | ||
| Last updated | 2016-03-15 | ||
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draft-li-idr-congestion-status-extended-community-00
IDR Z. Li
Internet-Draft China Mobile
Intended status: Standards Track J. Dong
Expires: September 16, 2016 Huawei Technologies
March 15, 2016
Carry congestion status in BGP extended community
draft-li-idr-congestion-status-extended-community-00
Abstract
A new extended community is introduced in this document to carry the
link congestion status, especially for the exit link of one AS. We
call this extended community congestion status community, which can
be used by the BGP routers to steer the Internet-access traffic among
the exit links by deploying policy routing.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 16, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Congestion Status Extended Community . . . . . . . . . . . . 4
2.1. Congestion Status Extended Community for Two-Octet AS . . 4
2.2. Congestion Status Extended Community for Four-Octet AS . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
typically the architecture of a large scale ISP's network is multi-
layered, as illustrated in Figure 1. The national backbone network
has its own AS, and each of the province or state network has a
specific AS. Backbone network connects all the province or state
networks together and has several exit links to access the Internet.
In some circumstances, the province or state network may have direct
exit links to the Internet. The total bandwidth of the backbone exit
links is usually much bigger than that of the direct exit links in
the province or state networks. Thus, the Internet-access traffic is
mainly transported through the backbone exit links by deploying route
policies on the ASBR routers in the province or state networks. The
ASBR routers in the province or state networks, for example, prefer
the routes learned from the backbone by setting higher local
preference for those routes. However, when the backbone exit links
are congested due to traffic increasing or delay of the capacity
expansion, the ASBR routers in the province or state networks do not
know this, and still delivery Internet-access traffic to the
backbone. The customer experience deteriorates, the operator, in
turn, will receive more and more complaints for its bad network
performance. Then, the operator has to steer some Internet-access
traffic to the direct exit links in the province or state networks by
deploying route policy on the ASBR routers. This kind of policy
should be removed when the capacity expansion of the backbone exit
links is done. The ASBR routers do not konw this again.
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+---------------------------------------------------------+
| |
| Internet |
| +----------+ +----------+ +----------+ |
+-| Router a |----------| Router b |---------| Router c |-+
+----------+ +----------+ +----------+
/ \ \ /
---/-----\-------------------\------------------/----------
| \ \ /ISP Network
| +----------+ +----------+ +----------+
| +-| Router 1 |----| Router 2 |----| Router 3 |-+
| | +----------+ +----------+ +----------+ |
| | |
| | BACKBONE |
| | AS B |
| | +----------+ +----------+ +----------+ |
| +-| Router L |----| Router M |----| Router N |-+
| +----------+ +----------+ +----------+
| / | \
| / | \
+----------+ +----------+ +----------+
+-| Router X |-+ +-| Router Y |-+ +-| Router Z |-+
| +----------+ | | +----------+ | | +----------+ |
| province X | | province Y | | province Z |
| AS X | | AS Y | | AS Z |
+--------------+ +--------------+ +--------------+
Figure 1
This document introduces a new extended community [RFC4360] to
delivery the congestion status of the exit link to other BGP peers.
The BGP receiver can then use this community to deploy route policy,
thus steer Internet-access traffic according to the congestion status
of the exit link. Router X in the above figure, for example, can
steer some Internet-access traffic to the direct exit link when it
knows the backbone exit link is congested. The introduced community
is called congestion status extended community.
Congestion status extended community is good not only to the ASBRs in
other AS, but also to the BGP peers within one AS. For instance,
Router M in backbone AS chooses Router 2 to transport the Internet-
access traffic by default. When Router M receives congestion status
extended communities from Router 1,2,3, which indicate the
utilization of the exit link of Router 1,2,3 is 90%, 70%, and 50%
respectively, it can choose Router 3 to transport some Internet-
access traffic using route policy.
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2. Congestion Status Extended Community
As described in [RFC4360], the extended community attribute is an
8-octet value with the first one or two octets to indicate the type
of this attribute. Since congestion status extended community needs
to be delivered from on AS to other ASes, and used by the BGP
speakers both in other ASes and within the same AS as the sender, it
MUST be a transitive extended community, i.e. the T bit in the first
octet MUST be zero.
Congestion status extended community has two encoding formats, one is
for two-octet AS, the other is for four-octet AS.
2.1. Congestion Status Extended Community for Two-Octet AS
Congestion status extended community for two-octet AS is a sub-type
allocated from Transitive Two-Octet AS-Specific Extended Community
Sub-Types defined in section 5.2.2 of [RFC7153]. Its format is as
Figure 2.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x00 | Sub-Type | Sender AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Bandwidth | Utilization |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
The "Type" field MUST be 0x00, which indicate this is a Transitive
Two-Octet AS-Specific Extended Community.
The "Sub-Type" field is used to indicate this is a Congestion
Status Extended Community. Its value is to be assigned by IANA.
0x06 is suggested.
The "Sender AS Number" field is 2 octets. Its value is the AS
number of the BGP speaker who generates this congestion status
extended community. The generator MUST have 2-octct AS number.
The "Reserved" field is 2 octets. This field is used to align
with the Congestion Status Extended Community for Four-Octet AS
defined in the next section of this document. Its value SHOULD be
zero. The BGP peers who receive this community MUST ignore this
field.
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The "Bandwidth" field is 1 octet. Its value is the bandwidth of
the exit link in unit of gbps (gigabits per second).
The "Utilization" field is 1 octet. Its value is the utilization
of the exit link in unit of percent. We can use the "Utilization"
field together with the "Bandwidth" field to calculate the traffic
load that we can further steer to this exit link.
2.2. Congestion Status Extended Community for Four-Octet AS
Congestion status extended community for four-octet AS is a sub-type
allocated from Transitive Four-Octet AS-Specific Extended Community
Sub-Types defined in section 5.2.4 of [RFC7153]. Its format is as
Figure 3.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x02 | Sub-Type | Sender AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender AS Number (cont.) | Bandwidth | Utilization |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3
The "Type" field MUST be 0x02, which indicate this is a Transitive
Four-Octet AS-Specific Extended Community.
The "Sub-Type" field is used to indicate this is a Congestion
Status Extended Community. Its value is to be assigned by IANA.
0x06 is suggested.
The "Sender AS Number" field is 4 octets. Its value is the AS
number of the BGP speaker who generates this congestion status
extended community. The generator MUST have 4-octct AS number.
The "Bandwidth" field is 1 octet. Its value is the bandwidth of
the exit link in unit of gbps (gigabits per second).
The "Utilization" field is 1 octet. Its value is the utilization
of the exit link in unit of percent. We can use the "Utilization"
field together with the "Bandwidth" field to calculate the traffic
load that we can further steer to this exit link.
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3. Security Considerations
Malicious router may use the congestion status extended community to
interfere the traffic steering decision of the BGP receiver. BGP
peers SHOULD use MD5 for authentication [RFC4360]. BGP receiver
SHOULD only accept the congestion status community or extended
community delivered from BGP peers with MD5 authentication.
4. IANA Considerations
One sub-type is solicited to be assigned from Transitive Two-Octet
AS-Specific Extended Community Sub-Types registry to indicate the
extended community with Type 0x00 is a Congestion Status Extended
Community for Two-Octet AS. 0x06 is suggested.
One sub-type is solicited to be assigned from Transitive Four-Octet
AS-Specific Extended Community Sub-Types registry to indicate the
extended community with Type 0x02 is a Congestion Status Extended
Community for Four-Octet AS. 0x06 is suggested.
5. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
February 2006, <http://www.rfc-editor.org/info/rfc4360>.
[RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP
Extended Communities", RFC 7153, DOI 10.17487/RFC7153,
March 2014, <http://www.rfc-editor.org/info/rfc7153>.
Authors' Addresses
Zhenqiang Li
China Mobile
No.32 Xuanwumenxi Ave., Xicheng District
Beijing 100032
P.R. China
Email: li_zhenqiang@hotmail.com
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Jie Dong
Huawei Technologies
Huawei Campus, No.156 Beiqing Rd.
Beijing 100095
P.R. China
Email: jie.dong@huawei.com
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